PRIDE CHEKERAsupermassive black hole called Sagittarius A. Some active
galaxies, called quasars, are powered by these supermassive
galaxies of millions solar masses. Most of the galaxies in our
universe have black holes at their central nuclei but they are
dormant unlike in quasars. About Sagittarius A, matter is just
orbiting the black holes without spiraling in. In quasars, matter
spirally accelerates into the black holes; as it falls in, it is heated
to very high temperatures about the accretion disc. Thus quasars
emit high energetic jets of X-rays, gamma rays and other highly
energetic radiations. M87 (NGC 4486) in the Virgo cluster is an
example of an active galaxies powered by a supermassive black
hole, 60 million light years away and also NGC 4261, 100
million light years away, in Virgo cluster. Quasars are sources of
some of the radio signals which astronomers always listen to.
Physicists thought black holes were like black bodies, absorbing
all radiation incident on them, hardly emitting any. This was so
until 1970s when Stephen Hawking and Bekenstein discovered
that black holes were not really black, but are thermal, emitting
a.k.a Hawking radiation due to quantum effects about the event
horizon of the black hole. Hawking and Bekenstein computed
that objects can orbit a black hole with certain angular
momentum provided those objects are far enough not to be
sucked by the ‘greedy’ black hole due to its very strong gravity.
If the object comes nearer enough it will spiral accelerating
towards the black hole’s event horizon. Since angular